1. Field of the Invention
This invention relates, generally, to endotracheal tubes. More particularly, it relates to an endotracheal tube having utility in surgical procedures requiring that one lung remain ventilated.
2. Description of the Prior Art
The human trachea has an elongate straight section that bifurcates into two branches, known as the left bronchus and the right bronchus, that respectively lead to the left and right lungs.
In surgical procedures involving parts of the body other than the lungs, an endotracheal tube is introduced into the trachea such that the leading end of the tube is positioned at a location, known as the carina, which is upstream of the left and right bronchus. A balloon-like member near the leading end of the endotracheal tube is then inflated to prevent air from the atmosphere from entering into the patient's lungs. Anesthesia and oxygen are then introduced into the patient's lungs through the endotracheal tube. In this way, the patient's breathing and the administration rate of anesthesia is under the control of an anesthesiologist. When the procedure is over and the patient is ready to be brought off of anesthesia, the balloon-like member is deflated and the endotracheal tube is withdrawn.
However, if a lung is to be operated upon, it must be shut down. The other lung must therefore be ventilated to keep the patient breathing. The ventilation of one lung while the other lung is shut down is known as one lung ventilation.
One lung ventilation is difficult to achieve with a conventional endotracheal tube because such tubes are straight in configuration. They are designed to go straight down the trachea to the carina and are not intended to be inserted into the left or right bronchus. However, the angle between the trachea and the right bronchus is not very sharp, and a skilled surgeon can usually introduce the leading end of an endotracheal tube into the right bronchus. This blocks off atmospheric air to the left bronchus, thereby shutting down the left lung. The balloon-like member is then inflated and anesthesia and oxygen are introduced into the right lung to keep it working while the surgeon operates on the left lung.
The angle between the trachea and the left bronchus is much sharper, however, and a conventional endotracheal tube cannot be introduced into the left bronchus with the same relative ease as the right bronchus. Accordingly, a conventional endotracheal tube cannot be used when a patient's left lung is to be ventilated while the right lung is shut down.
In response to this limitation, earlier inventors developed special endotracheal tubes that are capable of being inserted into the left or right bronchus. The one that has achieved commercial success is extraordinarily expensive; a common endotracheal tube costs less than ten dollars but the one in common use for one lung ventilation procedures costs about two hundred fifty dollars. It is a tube-in-tube structure where the inner, smaller tube is pushed to the side of the operated-upon lung to enable its introduction into the left or right bronchus. In use, the inner tube protrudes beyond the distal end of the outer or main tube; the main tube delivers oxygen and gas. A solid ball-like member is mounted at the distal end of the inner tube to close off the bronchus to be shut down. The outer tube has a diameter sufficient to accomplish adequate ventilation of the unoperated side.
One major drawback of this well-known tube, other than its expense, is the fact that the tube-in-tube arrangement restricts the flow of anesthesia into the ventilated lung and produces turbulence, requiring the anesthesiologist to make adjustments in the gas flows.
What is needed is an inexpensive endotracheal tube that facilitates its introduction into a left or right bronchus and which performs just like a conventional endotracheal tube so that an anesthesiologist may use it in the same manner as a conventional endotracheal tube, in the absence of a need to adjust flow rates to accommodate restrictions.
However, it was not obvious to those of ordinary skill in this art how the needed improvements could be provided, in view of the art considered as a whole at the time the present invention was made.